1. Field of the Invention
The present invention relates to a high-pressure processing apparatus optimally used, for example, to efficiently clean an object to be processed having a fine unevenness on the outer surface (microstructured surface) such as a semiconductor wafer or a semiconductor substrate and, for example, to a high-pressure processing apparatus installed in a clean room and used to peel off and remove contaminants such as resists adhered to the outer surface of a wafer during a semiconductor production process. The present invention also relates to a high-pressure processing apparatus used for drying for removing moisture attached to the outer surface of a wafer and for development for removing unnecessary portions present on the outer surface of the wafer.
2. Description of the Related Art
In the case of forming a pattern using a resist during a semiconductor production process, a cleaning step is essential to remove unnecessary and contaminant matters such as the resist which becomes unnecessary after the formation of the pattern and an etching polymer which is created during etching and remains on the wafer from the wafer.
Since the semiconductor production process is performed in a clean room, it is desirable to also perform the cleaning step in the clean room. However, it is costly not only to build the clean room, but also to maintain it. Thus, a cleaning apparatus is required to have a small installation area and excellent function and cleaning ability.
Conventionally, a wet cleaning unit according to which a semiconductor wafer or the like is immersed in a peeling liquid (cleaning liquid) and then rinsed with an alcohol or super pure water has been adopted as a semiconductor wafer cleaning method. Organic and inorganic compounds have been used as a peeling liquid. However, there have been problems that the peeling liquid cannot enter recessed portions of the fine pattern due to high surface tension and viscosity of the liquid, projected portions of the pattern are destroyed due to a capillary force created on a gas-liquid interface when the peeling liquid or a rinsing liquid are dried and a cubic expansion resulting from heating at the time of drying. Thus, the use of a fluid having a low viscosity such as supercritical carbon dioxide as the peeling liquid or the rinsing liquid has been recently studied.
For example, Japanese Unexamined Patent Publication No. 5(HEI)-226311 discloses a cleaning apparatus installable in a clean room and used to dissolve and remove contaminants such as moisture, fats and esters on the outer surface of a semiconductor wafer in a supercritical fluid. If carbon dioxide which easily evaporates at an atmospheric pressure, is excellent in safety, and inexpensive is used as a high-pressure or supercritical fluid, a carbon dioxide fluid can easily remove the moisture and fats on the outer surface of the wafer as disclosed in the above publication since having about as large a dissolving power as hexane, but a power thereof to dissolve polymer contaminants such as resists and etching polymers is insufficient. Thus, it is difficult to peel and remove these contaminants only by the carbon dioxide. Therefore, it is desirable to peel and remove polymer contaminants by adding a chemical liquid to the carbon dioxide.
On the other hand, for a more efficient cleaning step, a plurality of high-pressure processing chambers capable of performing cleaning while holding a high-pressure fluid should be provided and objects to be processed should be cleaned in the respective chambers. However, there is no consideration in the above publication No. 5-226311 about an apparatus which can precisely supply a high-pressure fluid and a chemical liquid to the respective chambers and is so designed to have a small installation area.
Further, in the case that a plurality of chambers are provided and different steps are performed in the respective chambers, supplied amounts of the high-pressure fluid differ according to a time table. Thus, a difficulty to properly maintain the pressure in the entire apparatus and a difficulty to stably perform the individual operations have been found out as problems.
In view of the problems residing in the prior art, an object of the present invention is to provide a high-pressure processing apparatus which has such a compact construction as to have part thereof installed in a clean room and can stably perform a high-pressure processing.